Adaptation of energy metabolism of overweight women to alternating and continuous low energy intake.

To investigate whether a slimming diet based on alternating (low with normal) energy intakes could counteract a decrease in energy requirement, 24-h energy expenditure (24EE), sleeping energy expenditure (sleeping EE), and physical activity were determined in a respiration chamber in 27 overweight women: before weight reduction and after 4 and 8 wk of slimming. Daily alternating and continuous slimming diets were supplied. Average weight losses over 8 wk of slimming were 6.9-9.0 kg. After 8 wk at low energy intake, 24EE had declined by 12-16% (from 2328 +/- 219 to 1987 +/- 204 kcal, mean +/- SD). Sleeping EE had declined by 7-13% (from 64 +/- 6 to 57 +/- 6 kcal/h). Measurements of physical activity indicated a reduction of spontaneous physical activity during slimming. Alternating low energy intake did not prevent 24EE from declining. The reduction in 24EE was determined by a decrease of body weight, dietary induced thermogenesis (in proportion to caloric restriction), and physical activity. There seems little reason to consider other adaptive mechanisms.